I have a 2 3D layers on a comp with a camera looking at them.
One 3D solid is masked out to be lit up by a pink light. In front of it is a QuickTime masked out to look like an old TV. The solid is acting like the ground, the pink light is acting like the TV brightness.
How do I make the opacity of the solid react to the brightness of the TV through an expression. I can't link it to the light b/c I don't have anything free to add an expression to. Everything is being used. All I have is the opacity of the solid. I tried adding Levels to the QT, but the Opacity expression won't link to the Histogram.